In some sewing operations, it is desirable to secure lace, tape or the like to a workpiece edge. In such an operation, the tape or lace is usually drawn from a continuous roll and thereafter progressively fed in a superimposed relationship with the workpiece to and through the machine's sewing station. Upon sewing tape or lace to the workpiece, it becomes necessary to sever the sewn on tape between successive workpiece or garments. Also, in most operations, it is imperative to sever the tape substantially co-extensive with the workpiece edge to which it is sewn.
It is well known to provide a sewing machine with a tape cutter for accomplishing this general purpose. Exemplary of such machines is the apparatus disclosed in U.S. Pat. No. 1,958,132 to H. L. Davis and granted May 8, 1934. The disadvantage with this type of cutting device, however, is that the cutting device is positioned an extended distance beyond the stitch forming instrumentality. Thus, there may be a length of tape which extends from the workpieces subsequent to the tape being cut. This excess tape is waste and requires subsequent, costly operations to produce an acceptable garment. Some of these machines have been known to employ mechanical sensors for detecting the workpiece. Mechanical sensor arrangements, however, have been known to be particularly sensitive and/or delicate and are susceptible to malfunctioning thus resulting in possible faulty operation of the cutting apparatus.
In contrast to mechanical sensors, it is known to use optical like sensor arrangements for detecting the workpiece. Exemplary of such devices is the arrangement shown in U.S. Pat. No. 2,881,833 to J. M. Hoffee granted Apr. 14, 1959. Such optical sensors, however, also have drawbacks. That is, optical sensors are usually sensitive to light dispersion and differing material density. Further, many optical sensors or scanners are sensitive to ambient light. Such susceptibility may result in the faulty operation of the tape severing apparatus. Furthermore, the environment in which this type of apparatus finds utility is usually laden with dust and lint, both of which may also effect the efficiency of such sensors. Furthermore, a photocell arrangement is usually not employed in close proximity to the sewing area because of the vibratory characteristics of the machine operation.
German Pat. No. 2,209,238 granted to Triumph International A.G. reveals an attempt at solving the problem of locating a tape cutter in close proximity to the sewing instrumentalities. This patent discloses a tape cutting apparatus which employs a blade and anvil for severing the tape. With this apparatus, however, an increased cutting force is required to sever the tape because of the single acting blade. Because of only one blade and to assure severance of the tape, a longer time is required to cut through the tape. Because of its proximity to the stitch forming instrumentalities, the longer cutting period effects the uniform work flow and, hence, the quality of the stitches being produced. Thus, there is a distinct advantage in extending the cutting period when the cutting apparatus is disposed in close proximity to the stitch forming instrumentalities.